The present invention relates to an internal combustion engine equipped with a sub-suction path to generate a swirl of suction gas in the combustion chamber.
Lately, internal combustion engines for automobiles are increasingly required not only to have the exhaust gas purified but also to improve the rate of fuel consumption.
To meet this demand, EGR (exhaust gas recirculation) and lean burning are often practiced and thereby it is known that for the purpose of filling both requirements of much EGR and lean burning and avoiding both misfiring and fluctuations in burning, the speed of combustion has only to be elevated.
Recently several proposals have been made for the purpose of elevating the speed of combustion to provide a sub-suction path apart from the main suction path so that a gas can be injected via said sub-suction path into the combustion chamber, thereby generating a swirl of the suction gas in the combustion chamber.
However, engines equipped with such a sub-suction path are still in the stage of transition to the practical application with many of the problems left to be solved in future. One problem is associated with the gas injection from the sub-suction path; it is desirable that, depending on the engine working conditions, the volume of gas injection be controlled, namely, little gas injection in time of idling and much in urban operation involving much EGR (under light or medium load operation).
Such a requirement may be satisfied for instance by connecting a negative pressure type or electronic type flow control valve to the sub-suction path, but this would make the mechanism complicated and be expensive.